#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int  fol(int n)
{
	if (n < 2)
		return n;
	else
		return 2 * fol(n - 1) + fol(n - 2);
}
int main()
{
	int n = 5;
	int ret = fol(n);
	printf("%d ", ret);
	return 0;
}